| |
| |
| Notes about the EGL library: |
| |
| |
| The EGL code here basically consists of two things: |
| |
| 1. An EGL API dispatcher. This directly routes all the eglFooBar() API |
| calls into driver-specific functions. |
| |
| 2. Fallbacks for EGL API functions. A driver _could_ implement all the |
| EGL API calls from scratch. But in many cases, the fallbacks provided |
| in libEGL (such as eglChooseConfig()) will do the job. |
| |
| |
| |
| Bootstrapping: |
| |
| When the apps calls eglOpenDisplay() a device driver is selected and loaded |
| (look for dlsym() or LoadLibrary() in egldriver.c). |
| |
| The driver's _eglMain() function is then called. This driver function |
| allocates, initializes and returns a new _EGLDriver object (usually a |
| subclass of that type). |
| |
| As part of initialization, the dispatch table in _EGLDriver->API must be |
| populated with all the EGL entrypoints. Typically, _eglInitDriverFallbacks() |
| can be used to plug in default/fallback functions. Some functions like |
| driver->API.Initialize and driver->API.Terminate _must_ be implemented |
| with driver-specific code (no default/fallback function is possible). |
| |
| |
| A bit later, the app will call eglInitialize(). This will get routed |
| to the driver->API.Initialize() function. Any additional driver |
| initialization that wasn't done in _eglMain() should be done at this |
| point. Typically, this will involve setting up visual configs, etc. |
| |
| |
| |
| Special Functions: |
| |
| Certain EGL functions _must_ be implemented by the driver. This includes: |
| |
| eglCreateContext |
| eglCreateWindowSurface |
| eglCreatePixmapSurface |
| eglCreatePBufferSurface |
| eglMakeCurrent |
| eglSwapBuffers |
| |
| Most of the EGLConfig-related functions can be implemented with the |
| defaults/fallbacks. Same thing for the eglGet/Query functions. |
| |
| |
| |
| |
| Teardown: |
| |
| When eglTerminate() is called, the driver->API.Terminate() function is |
| called. The driver should clean up after itself. eglTerminate() will |
| then close/unload the driver (shared library). |
| |
| |
| |
| |
| Subclassing: |
| |
| The internal libEGL data structures such as _EGLDisplay, _EGLContext, |
| _EGLSurface, etc should be considered base classes from which drivers |
| will derive subclasses. |
| |
